The grueling construction on Interstate 35E through Denton County isn't finished yet. But Saturday marks a milestone in the multibillion-dollar rebuild of the major north-south corridor. That's when the new bridge over Lewisville Lake opens to southbound traffic.

Accidents and traffic snarls along the old bridges have typically turned into nightmares.

But by 8 a.m. Saturday, that will begin to change. That's when southbound drivers will be able to use the new bridge that's parallel to the existing highway span over the lake. By the end of next week, northbound traffic will also be moved onto the new bridge.

Once that happens, Texas Department of Transportation crews will reconfigure the existing bridges. But one remaining lane of the existing bridge will act as the northbound exit to Lake Dallas Drive.

Several state and regional officials commemorated the milestone at a ceremony and caravan over the bridge Wednesday.

Eventually, the new bridge will carry two southbound frontage road lanes, four southbound main lanes and two reversible managed lanes. It will also have a pedestrian and bicycle path. Once the existing bridges are reconfigured, they will carry two northbound frontage road lanes, four northbound main lanes and a bicycle and pedestrian path.

That's an additional two frontage road lanes, one main lane, two reversible managed lanes and a bicycle and pedestrian path in each direction.

The work is part of the ongoing, $4.8 billion rebuild and expansion of the highway from LBJ Freeway in Dallas to U.S. Highway 380 in Denton. TxDOT is currently working on the $1.4 billion first phase, which includes some new bridges and intersections and rebuilding portions of the highway. That phase will be complete next year. The second and final phase will finish rebuilding that entire length, but funding has not yet been secured.